find the key associated with a value in a map in csharp

To find the key associated with a specific value in a Dictionary (which is the C# equivalent of a map), you can use LINQ to search for the first key that has the desired value:

main.cs
using System.Linq;

// declare and populate a dictionary of key-value pairs
Dictionary<string, int> myDict = new Dictionary<string, int>();
myDict.Add("apple", 1);
myDict.Add("orange", 2);
myDict.Add("banana", 3);

// search for the key associated with the value 2
string key = myDict.FirstOrDefault(x => x.Value == 2).Key;

Console.WriteLine(key); // output: "orange"
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In the above example, the FirstOrDefault method of the Dictionary is used with a lambda expression to search for the first key-value pair where the value is equal to 2. The Key property of that pair is then returned. If no matching key is found, null is returned.